Procedura: Caricare assembly nel contesto di sola reflection
Il contesto di caricamento di sola reflection consente di esaminare gli assembly compilati per altre piattaforme o per altre versioni di .NET. Il codice caricato in questo contesto può essere esaminato solo; non può essere eseguito. Ciò significa che gli oggetti non possono essere creati, perché i costruttori non possono essere eseguiti. Poiché il codice non può essere eseguito, le dipendenze non vengono caricate automaticamente. Per esaminarle, è necessario caricarle manualmente.
Per caricare un assembly nel contesto di caricamento di sola reflection
Usare l'overload del metodo ReflectionOnlyLoad(String) per caricare l'assembly in base al nome di visualizzazione oppure il metodo ReflectionOnlyLoadFrom per caricare l'assembly in base al percorso. Se l'assembly è un'immagine binaria, usare l'overload del metodo ReflectionOnlyLoad(Byte[]).
Nota
Non è possibile usare il contesto di sola reflection per caricare una versione di mscorlib.dll da una versione di .NET Framework diversa dalla versione nel contesto di esecuzione.
Se l'assembly contiene dipendenze, queste ultime non verranno caricate dal metodo ReflectionOnlyLoad. Per esaminarle, è necessario caricarle manualmente.
Determinare se un assembly viene caricato nel contesto di sola reflection usando la proprietà ReflectionOnly dell'assembly.
Se all'assembly o ai tipi in esso contenuti sono applicati attributi, esaminare gli attributi usando la classe CustomAttributeData per assicurarsi che non venga effettuato alcun tentativo di eseguire il codice nel contesto di sola reflection. Usare l'overload appropriato del metodo CustomAttributeData.GetCustomAttributes per ottenere gli oggetti CustomAttributeData che rappresentano gli attributi applicati a un assembly, membro, modulo o parametro.
Nota
Gli attributi applicati all'assembly o al relativo contenuto possono essere definiti nell'assembly o in un altro assembly caricato nel contesto di sola reflection. Non è possibile stabilire in anticipo dove sono definiti gli attributi.
Esempio
L'esempio di codice seguente illustra come esaminare gli attributi applicati a un assembly caricato nel contesto di sola reflection.
L'esempio di codice definisce un attributo personalizzato con due costruttori e una proprietà. L'attributo è applicato all'assembly, a un tipo dichiarato nell'assembly, a un metodo del tipo e a un parametro del metodo. Quando viene eseguito, l'assembly viene caricato nel contesto di sola reflection e vengono visualizzate informazioni sugli attributi personalizzati applicati all'assembly e ai tipi e membri che contiene.
Nota
Per semplificare l'esempio di codice, l'assembly carica ed esamina se stesso. In genere, non è probabile che lo stesso assembly venga caricato sia nel contesto di esecuzione che nel contesto di sola reflection.
using namespace System;
using namespace System::Reflection;
using namespace System::Collections::Generic;
using namespace System::Collections::ObjectModel;
// An enumeration used by the ExampleAttribute class.
public enum class ExampleKind
{
FirstKind, SecondKind, ThirdKind, FourthKind
};
// An example attribute. The attribute can be applied to all
// targets, from assemblies to parameters.
//
[AttributeUsage(AttributeTargets::All)]
public ref class ExampleAttribute: public Attribute
{
private:
// Data for properties.
ExampleKind kindValue;
String^ noteValue;
array<String^>^ arrayStrings;
array<int>^ arrayNumbers;
// Constructors.
void ExampleAttributeInitialize( ExampleKind initKind, array<String^>^ initStrings )
{
kindValue = initKind;
arrayStrings = initStrings;
}
public:
ExampleAttribute()
{
ExampleAttributeInitialize( ExampleKind::FirstKind, nullptr );
}
ExampleAttribute( ExampleKind initKind )
{
ExampleAttributeInitialize( initKind, nullptr );
}
ExampleAttribute( ExampleKind initKind, array<String^>^ initStrings )
{
ExampleAttributeInitialize( initKind, initStrings );
}
// Properties. The Note and Numbers properties must be read/write, so they
// can be used as named parameters.
//
property ExampleKind Kind
{
ExampleKind get()
{
return kindValue;
}
}
property array<String^>^ Strings
{
array<String^>^ get()
{
return arrayStrings;
}
}
property String^ Note
{
String^ get()
{
return noteValue;
}
void set( String^ value )
{
noteValue = value;
}
}
property array<int>^ Numbers
{
array<int>^ get()
{
return arrayNumbers;
}
void set( array<int>^ value )
{
arrayNumbers = value;
}
}
};
// The example attribute is applied to the assembly.
[assembly:Example(ExampleKind::ThirdKind,Note="This is a note on the assembly.")];
// The example attribute is applied to the test class.
//
[Example(ExampleKind::SecondKind,
gcnew array<String^> { "String array argument, line 1",
"String array argument, line 2",
"String array argument, line 3" },
Note="This is a note on the class.",
Numbers = gcnew array<int> { 53, 57, 59 })]
public ref class Test
{
public:
// The example attribute is applied to a method, using the
// parameterless constructor and supplying a named argument.
// The attribute is also applied to the method parameter.
//
[Example(Note="This is a note on a method.")]
void TestMethod( [Example] Object^ arg ){}
// Main() gets objects representing the assembly, the test
// type, the test method, and the method parameter. Custom
// attribute data is displayed for each of these.
//
static void Main()
{
Assembly^ assembly = Assembly::ReflectionOnlyLoad( "Source" );
Type^ t = assembly->GetType( "Test" );
MethodInfo^ m = t->GetMethod( "TestMethod" );
array<ParameterInfo^>^p = m->GetParameters();
Console::WriteLine( "\r\nAttributes for assembly: '{0}'", assembly );
ShowAttributeData( CustomAttributeData::GetCustomAttributes( assembly ) );
Console::WriteLine( "\r\nAttributes for type: '{0}'", t );
ShowAttributeData( CustomAttributeData::GetCustomAttributes( t ) );
Console::WriteLine( "\r\nAttributes for member: '{0}'", m );
ShowAttributeData( CustomAttributeData::GetCustomAttributes( m ) );
Console::WriteLine( "\r\nAttributes for parameter: '{0}'", p );
ShowAttributeData( CustomAttributeData::GetCustomAttributes( p[ 0 ] ) );
}
private:
static void ShowValueOrArray(CustomAttributeTypedArgument^ cata)
{
if (cata->Value->GetType() == ReadOnlyCollection<CustomAttributeTypedArgument>::typeid)
{
Console::WriteLine(" Array of '{0}':", cata->ArgumentType);
for each (CustomAttributeTypedArgument^ cataElement in
(ReadOnlyCollection<CustomAttributeTypedArgument>^) cata->Value)
{
Console::WriteLine(" Type: '{0}' Value: '{1}'",
cataElement->ArgumentType, cataElement->Value);
}
}
else
{
Console::WriteLine( " Type: '{0}' Value: '{1}'",
cata->ArgumentType, cata->Value );
}
}
static void ShowAttributeData( IList< CustomAttributeData^ >^ attributes )
{
for each ( CustomAttributeData^ cad in attributes )
{
Console::WriteLine( " {0}", cad );
Console::WriteLine( " Constructor: '{0}'", cad->Constructor );
Console::WriteLine( " Constructor arguments:" );
for each ( CustomAttributeTypedArgument^ cata in cad->ConstructorArguments )
{
ShowValueOrArray(cata);
}
Console::WriteLine( " Named arguments:" );
for each ( CustomAttributeNamedArgument cana in cad->NamedArguments )
{
Console::WriteLine( " MemberInfo: '{0}'", cana.MemberInfo );
ShowValueOrArray(cana.TypedValue);
}
}
}
};
int main()
{
Test::Main();
}
/* This code example produces output similar to the following:
Attributes for assembly: 'source, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
[System.Runtime.CompilerServices.CompilationRelaxationsAttribute((Int32)8)]
Constructor: 'Void .ctor(Int32)'
Constructor arguments:
Type: 'System.Int32' Value: '8'
Named arguments:
[System.Runtime.CompilerServices.RuntimeCompatibilityAttribute(WrapNonExceptionThrows = True)]
Constructor: 'Void .ctor()'
Constructor arguments:
Named arguments:
MemberInfo: 'Boolean WrapNonExceptionThrows'
Type: 'System.Boolean' Value: 'True'
[ExampleAttribute((ExampleKind)2, Note = "This is a note on the assembly.")]
Constructor: 'Void .ctor(ExampleKind)'
Constructor arguments:
Type: 'ExampleKind' Value: '2'
Named arguments:
MemberInfo: 'System.String Note'
Type: 'System.String' Value: 'This is a note on the assembly.'
Attributes for type: 'Test'
[ExampleAttribute((ExampleKind)1, new String[3] { "String array argument, line 1", "String array argument, line 2", "String array argument, line 3" }, Note = "This is a note on the class.", Numbers = new Int32[3] { 53, 57, 59 })]
Constructor: 'Void .ctor(ExampleKind, System.String[])'
Constructor arguments:
Type: 'ExampleKind' Value: '1'
Array of 'System.String[]':
Type: 'System.String' Value: 'String array argument, line 1'
Type: 'System.String' Value: 'String array argument, line 2'
Type: 'System.String' Value: 'String array argument, line 3'
Named arguments:
MemberInfo: 'System.String Note'
Type: 'System.String' Value: 'This is a note on the class.'
MemberInfo: 'Int32[] Numbers'
Array of 'System.Int32[]':
Type: 'System.Int32' Value: '53'
Type: 'System.Int32' Value: '57'
Type: 'System.Int32' Value: '59'
Attributes for member: 'Void TestMethod(System.Object)'
[ExampleAttribute(Note = "This is a note on a method.")]
Constructor: 'Void .ctor()'
Constructor arguments:
Named arguments:
MemberInfo: 'System.String Note'
Type: 'System.String' Value: 'This is a note on a method.'
Attributes for parameter: 'System.Object arg'
[ExampleAttribute()]
Constructor: 'Void .ctor()'
Constructor arguments:
Named arguments:
*/
using System;
using System.Reflection;
using System.Collections.Generic;
using System.Collections.ObjectModel;
// The example attribute is applied to the assembly.
[assembly:Example(ExampleKind.ThirdKind, Note="This is a note on the assembly.")]
// An enumeration used by the ExampleAttribute class.
public enum ExampleKind
{
FirstKind,
SecondKind,
ThirdKind,
FourthKind
};
// An example attribute. The attribute can be applied to all
// targets, from assemblies to parameters.
//
[AttributeUsage(AttributeTargets.All)]
public class ExampleAttribute : Attribute
{
// Data for properties.
private ExampleKind kindValue;
private string noteValue;
private string[] arrayStrings;
private int[] arrayNumbers;
// Constructors. The parameterless constructor (.ctor) calls
// the constructor that specifies ExampleKind and an array of
// strings, and supplies the default values.
//
public ExampleAttribute(ExampleKind initKind, string[] initStrings)
{
kindValue = initKind;
arrayStrings = initStrings;
}
public ExampleAttribute(ExampleKind initKind) : this(initKind, null) {}
public ExampleAttribute() : this(ExampleKind.FirstKind, null) {}
// Properties. The Note and Numbers properties must be read/write, so they
// can be used as named parameters.
//
public ExampleKind Kind { get { return kindValue; }}
public string[] Strings { get { return arrayStrings; }}
public string Note
{
get { return noteValue; }
set { noteValue = value; }
}
public int[] Numbers
{
get { return arrayNumbers; }
set { arrayNumbers = value; }
}
}
// The example attribute is applied to the test class.
//
[Example(ExampleKind.SecondKind,
new string[] { "String array argument, line 1",
"String array argument, line 2",
"String array argument, line 3" },
Note="This is a note on the class.",
Numbers = new int[] { 53, 57, 59 })]
public class Test
{
// The example attribute is applied to a method, using the
// parameterless constructor and supplying a named argument.
// The attribute is also applied to the method parameter.
//
[Example(Note="This is a note on a method.")]
public void TestMethod([Example] object arg) { }
// Main() gets objects representing the assembly, the test
// type, the test method, and the method parameter. Custom
// attribute data is displayed for each of these.
//
public static void Main()
{
Assembly asm = Assembly.ReflectionOnlyLoad("Source");
Type t = asm.GetType("Test");
MethodInfo m = t.GetMethod("TestMethod");
ParameterInfo[] p = m.GetParameters();
Console.WriteLine("\r\nAttributes for assembly: '{0}'", asm);
ShowAttributeData(CustomAttributeData.GetCustomAttributes(asm));
Console.WriteLine("\r\nAttributes for type: '{0}'", t);
ShowAttributeData(CustomAttributeData.GetCustomAttributes(t));
Console.WriteLine("\r\nAttributes for member: '{0}'", m);
ShowAttributeData(CustomAttributeData.GetCustomAttributes(m));
Console.WriteLine("\r\nAttributes for parameter: '{0}'", p);
ShowAttributeData(CustomAttributeData.GetCustomAttributes(p[0]));
}
private static void ShowAttributeData(
IList<CustomAttributeData> attributes)
{
foreach( CustomAttributeData cad in attributes )
{
Console.WriteLine(" {0}", cad);
Console.WriteLine(" Constructor: '{0}'", cad.Constructor);
Console.WriteLine(" Constructor arguments:");
foreach( CustomAttributeTypedArgument cata
in cad.ConstructorArguments )
{
ShowValueOrArray(cata);
}
Console.WriteLine(" Named arguments:");
foreach( CustomAttributeNamedArgument cana
in cad.NamedArguments )
{
Console.WriteLine(" MemberInfo: '{0}'",
cana.MemberInfo);
ShowValueOrArray(cana.TypedValue);
}
}
}
private static void ShowValueOrArray(CustomAttributeTypedArgument cata)
{
if (cata.Value.GetType() == typeof(ReadOnlyCollection<CustomAttributeTypedArgument>))
{
Console.WriteLine(" Array of '{0}':", cata.ArgumentType);
foreach (CustomAttributeTypedArgument cataElement in
(ReadOnlyCollection<CustomAttributeTypedArgument>) cata.Value)
{
Console.WriteLine(" Type: '{0}' Value: '{1}'",
cataElement.ArgumentType, cataElement.Value);
}
}
else
{
Console.WriteLine(" Type: '{0}' Value: '{1}'",
cata.ArgumentType, cata.Value);
}
}
}
/* This code example produces output similar to the following:
Attributes for assembly: 'source, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
[System.Runtime.CompilerServices.CompilationRelaxationsAttribute((Int32)8)]
Constructor: 'Void .ctor(Int32)'
Constructor arguments:
Type: 'System.Int32' Value: '8'
Named arguments:
[System.Runtime.CompilerServices.RuntimeCompatibilityAttribute(WrapNonExceptionThrows = True)]
Constructor: 'Void .ctor()'
Constructor arguments:
Named arguments:
MemberInfo: 'Boolean WrapNonExceptionThrows'
Type: 'System.Boolean' Value: 'True'
[ExampleAttribute((ExampleKind)2, Note = "This is a note on the assembly.")]
Constructor: 'Void .ctor(ExampleKind)'
Constructor arguments:
Type: 'ExampleKind' Value: '2'
Named arguments:
MemberInfo: 'System.String Note'
Type: 'System.String' Value: 'This is a note on the assembly.'
Attributes for type: 'Test'
[ExampleAttribute((ExampleKind)1, new String[3] { "String array argument, line 1", "String array argument, line 2", "String array argument, line 3" }, Note = "This is a note on the class.", Numbers = new Int32[3] { 53, 57, 59 })]
Constructor: 'Void .ctor(ExampleKind, System.String[])'
Constructor arguments:
Type: 'ExampleKind' Value: '1'
Array of 'System.String[]':
Type: 'System.String' Value: 'String array argument, line 1'
Type: 'System.String' Value: 'String array argument, line 2'
Type: 'System.String' Value: 'String array argument, line 3'
Named arguments:
MemberInfo: 'System.String Note'
Type: 'System.String' Value: 'This is a note on the class.'
MemberInfo: 'Int32[] Numbers'
Array of 'System.Int32[]':
Type: 'System.Int32' Value: '53'
Type: 'System.Int32' Value: '57'
Type: 'System.Int32' Value: '59'
Attributes for member: 'Void TestMethod(System.Object)'
[ExampleAttribute(Note = "This is a note on a method.")]
Constructor: 'Void .ctor()'
Constructor arguments:
Named arguments:
MemberInfo: 'System.String Note'
Type: 'System.String' Value: 'This is a note on a method.'
Attributes for parameter: 'System.Object arg'
[ExampleAttribute()]
Constructor: 'Void .ctor()'
Constructor arguments:
Named arguments:
*/
Imports System.Reflection
Imports System.Collections.Generic
Imports System.Collections.ObjectModel
' The example attribute is applied to the assembly.
<Assembly: Example(ExampleKind.ThirdKind, Note:="This is a note on the assembly.")>
' An enumeration used by the ExampleAttribute class.
Public Enum ExampleKind
FirstKind
SecondKind
ThirdKind
FourthKind
End Enum
' An example attribute. The attribute can be applied to all
' targets, from assemblies to parameters.
'
<AttributeUsage(AttributeTargets.All)> _
Public Class ExampleAttribute
Inherits Attribute
' Data for properties.
Private kindValue As ExampleKind
Private noteValue As String
Private arrayStrings() As String
Private arrayNumbers() As Integer
' Constructors. The parameterless constructor (.ctor) calls
' the constructor that specifies ExampleKind and an array of
' strings, and supplies the default values.
'
Public Sub New(ByVal initKind As ExampleKind, ByVal initStrings() As String)
kindValue = initKind
arrayStrings = initStrings
End Sub
Public Sub New(ByVal initKind As ExampleKind)
Me.New(initKind, Nothing)
End Sub
Public Sub New()
Me.New(ExampleKind.FirstKind, Nothing)
End Sub
' Properties. The Note and Numbers properties must be read/write, so they
' can be used as named parameters.
'
Public ReadOnly Property Kind As ExampleKind
Get
Return kindValue
End Get
End Property
Public ReadOnly Property Strings As String()
Get
Return arrayStrings
End Get
End Property
Public Property Note As String
Get
Return noteValue
End Get
Set
noteValue = value
End Set
End Property
Public Property Numbers As Integer()
Get
Return arrayNumbers
End Get
Set
arrayNumbers = value
End Set
End Property
End Class
' The example attribute is applied to the test class.
'
<Example(ExampleKind.SecondKind, _
New String() {"String array argument, line 1", _
"String array argument, line 2", _
"String array argument, line 3"}, _
Note:="This is a note on the class.", _
Numbers:=New Integer() {53, 57, 59})> _
Public Class Test
' The example attribute is applied to a method, using the
' parameterless constructor and supplying a named argument.
' The attribute is also applied to the method parameter.
'
<Example(Note:="This is a note on a method.")> _
Public Sub TestMethod(<Example()> ByVal arg As Object)
End Sub
' Sub Main gets objects representing the assembly, the test
' type, the test method, and the method parameter. Custom
' attribute data is displayed for each of these.
'
Public Shared Sub Main()
Dim asm As [Assembly] = Assembly.ReflectionOnlyLoad("source")
Dim t As Type = asm.GetType("Test")
Dim m As MethodInfo = t.GetMethod("TestMethod")
Dim p() As ParameterInfo = m.GetParameters()
Console.WriteLine(vbCrLf & "Attributes for assembly: '{0}'", asm)
ShowAttributeData(CustomAttributeData.GetCustomAttributes(asm))
Console.WriteLine(vbCrLf & "Attributes for type: '{0}'", t)
ShowAttributeData(CustomAttributeData.GetCustomAttributes(t))
Console.WriteLine(vbCrLf & "Attributes for member: '{0}'", m)
ShowAttributeData(CustomAttributeData.GetCustomAttributes(m))
Console.WriteLine(vbCrLf & "Attributes for parameter: '{0}'", p)
ShowAttributeData(CustomAttributeData.GetCustomAttributes(p(0)))
End Sub
Private Shared Sub ShowAttributeData( _
ByVal attributes As IList(Of CustomAttributeData))
For Each cad As CustomAttributeData _
In CType(attributes, IEnumerable(Of CustomAttributeData))
Console.WriteLine(" {0}", cad)
Console.WriteLine(" Constructor: '{0}'", cad.Constructor)
Console.WriteLine(" Constructor arguments:")
For Each cata As CustomAttributeTypedArgument _
In CType(cad.ConstructorArguments, IEnumerable(Of CustomAttributeTypedArgument))
ShowValueOrArray(cata)
Next
Console.WriteLine(" Named arguments:")
For Each cana As CustomAttributeNamedArgument _
In CType(cad.NamedArguments, IEnumerable(Of CustomAttributeNamedArgument))
Console.WriteLine(" MemberInfo: '{0}'", _
cana.MemberInfo)
ShowValueOrArray(cana.TypedValue)
Next
Next
End Sub
Private Shared Sub ShowValueOrArray(ByVal cata As CustomAttributeTypedArgument)
If cata.Value.GetType() Is GetType(ReadOnlyCollection(Of CustomAttributeTypedArgument)) Then
Console.WriteLine(" Array of '{0}':", cata.ArgumentType)
For Each cataElement As CustomAttributeTypedArgument In cata.Value
Console.WriteLine(" Type: '{0}' Value: '{1}'", _
cataElement.ArgumentType, cataElement.Value)
Next
Else
Console.WriteLine(" Type: '{0}' Value: '{1}'", _
cata.ArgumentType, cata.Value)
End If
End Sub
End Class
' This code example produces output similar to the following:
'
'Attributes for assembly: 'source, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
' [System.Runtime.CompilerServices.CompilationRelaxationsAttribute((Int32)8)]
' Constructor: 'Void .ctor(Int32)'
' Constructor arguments:
' Type: 'System.Int32' Value: '8'
' Named arguments:
' [System.Runtime.CompilerServices.RuntimeCompatibilityAttribute(WrapNonExceptionThrows = True)]
' Constructor: 'Void .ctor()'
' Constructor arguments:
' Named arguments:
' MemberInfo: 'Boolean WrapNonExceptionThrows'
' Type: 'System.Boolean' Value: 'True'
' [ExampleAttribute((ExampleKind)2, Note = "This is a note on the assembly.")]
' Constructor: 'Void .ctor(ExampleKind)'
' Constructor arguments:
' Type: 'ExampleKind' Value: '2'
' Named arguments:
' MemberInfo: 'System.String Note'
' Type: 'System.String' Value: 'This is a note on the assembly.'
'
'Attributes for type: 'Test'
' [ExampleAttribute((ExampleKind)1, new String[3] { "String array argument, line 1", "String array argument, line 2", "String array argument, line 3" }, Note = "This is a note on the class.", Numbers = new Int32[3] { 53, 57, 59 })]
' Constructor: 'Void .ctor(ExampleKind, System.String[])'
' Constructor arguments:
' Type: 'ExampleKind' Value: '1'
' Array of 'System.String[]':
' Type: 'System.String' Value: 'String array argument, line 1'
' Type: 'System.String' Value: 'String array argument, line 2'
' Type: 'System.String' Value: 'String array argument, line 3'
' Named arguments:
' MemberInfo: 'System.String Note'
' Type: 'System.String' Value: 'This is a note on the class.'
' MemberInfo: 'Int32[] Numbers'
' Array of 'System.Int32[]':
' Type: 'System.Int32' Value: '53'
' Type: 'System.Int32' Value: '57'
' Type: 'System.Int32' Value: '59'
'
'Attributes for member: 'Void TestMethod(System.Object)'
' [ExampleAttribute(Note = "This is a note on a method.")]
' Constructor: 'Void .ctor()'
' Constructor arguments:
' Named arguments:
' MemberInfo: 'System.String Note'
' Type: 'System.String' Value: 'This is a note on a method.'
'
'Attributes for parameter: 'System.Object arg'
' [ExampleAttribute()]
' Constructor: 'Void .ctor()'
' Constructor arguments:
' Named arguments:
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